Grinding Shims.

I was wondering what you guys would make of this...
I phoned a place which does engine work, [not too many round here]and asked them about valve jobs.
The quote was reasonable, but a comment the guy made got me thinking[hurts, no...no].
He told me that they would shim the head,and would need the cams.
Scratched head, asked him what part they would shim,mentioning in passing that this head has under bucket shims:blink:
He tells me that they can source shims[which is RARE!]and then went on to say that if they couldn't get the correct shim that they would grind the existing one to get correct clearance.
I am aware that the KZ knowledge here is the best and would appreciate your comments.
I'm concerned because I was under the impression that these shims are case hardened and grinding them seems questionable to put it mildly.
Thanks in advance for any advice/comments.

This topic has been flogged pretty throughly on the other Ksaki forum, mainly because the 32mm shims for the twins are no longer available from ANYBODY and regularly get scalped for $15-20 each on ebay. If you need the 32mm shims, good luck. Z1 used to have a couple of izes available. If not, all you can do is go to the dealers on your hands and knees and beg.... and the dealer I bought my bike NEW from told me to push off when I asked to buy a shim.
FYI:

1) Most of the people say the shims ARE surface hardened. If so, they could be ground and used ONLY if ground only on one side, and only if the ground side was kept against the larger flat surface of the bucket, and NEVER put towards the valve stem.

2) One person who was a machinist said they cut some shims vertically and horizontally and saw no hardness variation in them.

I have one degree in mechanical engineering, and I do not understand how they could be made without surface hardening. I know from experience they are REALLY hard on the surface, and if they were that hard all the way through, they would shatter very easily. Just my opinion.

SPARKY47 wrote:

He told me that they would shim the head,and would need the cams.
Scratched head, asked him what part they would shim,mentioning in passing that this head has under bucket shims:blink:
He tells me that they can source shims[which is RARE!]and then went on to say that if they couldn't get the correct shim that they would grind the existing one to get correct clearance.

If your engine uses the 29mm shims, there are lots of them available. 32 mm and it's another story.

BTW: if they will take ownership of the shimming for a reasonable price, dump it right in their lap. You won't have to search the net for shims and keep pulling the cams on and off.

Bountyhunter, thanks for the info, $64000 question, would you be happy to have this done?
They're 13mm by the way.
Z500/4

I ground a couple of mine in on a surface grinder at work when I needed them asap and the dealer couldn't get them for 3-4days. Didn't see any extra wear on the surfaces of ground ones. After all your not taking off much material, just a few thou.

kxhonda,thankyou for your comments,out of curiosity, how often have you had to adjust valve clearances since the work was done?

SPARKY47 wrote:

Bountyhunter, thanks for the info, $64000 question, would you be happy to have this done?
They're 13mm by the way.
Z500/4

Not happy, but I would have had to do it if I hadn't been able to find the right 32mm shims for my 750 Twin. I did the next best thing: I measured the shims and gave the machine shop the allowable range of finished valve end heights that I could shim in with the shims I had or could get, and they hit them. They can probably do that with yours.

If you grind them, just make sure you mark the "ground" side and keep it towards the flat side of the bucket, and don't ever reverse it.

kxhonda wrote:

I ground a couple of mine in on a surface grinder at work when I needed them asap and the dealer couldn't get them for 3-4days. Didn't see any extra wear on the surfaces of ground ones. After all your not taking off much material, just a few thou.

Good point. If you are only shaving a few thou, it might be OK. I know that Smith-Wesson hammers and triggers are surface hardened to a depth of about .008". The shims might be similar, so a few thou off might be OK.

I have about 8 or so years in as a blacksmith...

I can see O-2, A-2, or 1050 to 1075 steel being used as a shim.

You would have to have a very precise jig to machine the surfaces perfectly flat. After all, you are pushing 10k+ RPMs.

I would use either a (compression) peening or combination of quick-quench hardening and chemical hardening to finish the surface.

I'd probably bake them for an hour or two @450F to take the curse out of it.

A precise polishing jig would hurt either, you don't want this thing anything but *perfectly* flat on both sides:unsure:

I think I'm going to end up making a couple.

beatpoet,if you decide to make a couple please start a thread to let us know your progress and outcome.

I have been podering turning my own shims on a lathe. I would have to make a special collet to hold the shim to face it's final thickness. I would tend to think that CR steel would be strong enough to remain dimensionally stable. I figured the factory shims are hardnened, but it may not be entirely necessary... just my late night thoughts.

Surface hardening is simply a matter of adding more carbon to the surface of the steel, to the needed depth. There is a commercial product called Kasenit, and Machinist Bedside Reader #2 has a story in it about how to make and use your own mixture for hardening. Both methods can be used at home, but a surface grinder is pretty much required to grind them to size.

It seems to me that grinding the tips of the valve stems to increase clearance would be a lot simpler, although there is a limit as to how far they can be ground.

As to grinding OEM shims and hardening, look at it this way, if they do wear due to insufficient hardening remaining, it's going to decrease the thickness of the shim, thus increasing the valve clearance, and the oil filter should catch any metal particles created by the wear. But I would only grind them on the side that contacts the valve bucket.

So I think worst case is you would have to adjust valve clearances sooner.